Since before the Second World War, the beverage industry has been packaging and selling beverages in aluminum cans. Over the years this industry has seen numerous innovations relating to can style and functionality, wherein the first generation of aluminum cans included “cone top” and “flat top” cans. True to their names, the cone top can included a conical top sealed off by a removable cap, while the flat top can included a flat top, which allowed beverage access using a device called a “church key,” which was basically a can opener used to puncture the top of the can. By 1960 cone top can production ceased, yielding to the popularity of the flat top can. Around this same time however, an innovation in the beverage can industry known as the “zip top” or “pull tab,” was developed, and threatened to overtake the flat top's market hold. The zip top allowed a user to grasp a metallic tab attached to a spout shaped portion of the can top and pull the tab and portion of the top completely off of the can, creating a can opening which allowed access to the contents within. The convenience of the zip top can was readily apparent, and by the late 1960's the flat top can was starting to be replaced by the zip top can.
Although the zip top can was convenient an most likely boosted beverage can sales in general, it also had a couple of disadvantages. First of all, the loose pull tabs which came off the cans were damaging to the environment. Pets and wildlife died from ingesting pull tabs, as did more than a few people who dropped them into their beverage can and accidentally choked on them. Moreover, these tabs not only wound up on beaches, where beachgoers cut their feet on them, they also littered roadsides and damaged garbage disposals. One response to address these disadvantages involved the development of the “stay tab.”
Introduced in 1975, the stay tab was designed to stay connected to the can. The tab is essentially hinged to the top of a can in a manner that allows a consumer to pull up on a ring end of the tab, causing the opposite end of the tab to press down on a perforated portion of the top of the can. As the ring end of the tab is pulled upward, the opposite end pierces the can top along the perforation, remaining with the can until recycling/disposal. While the metal attaching the tab to the can top bends to allow piercing of the perforation, it does not readily break off the top of the can, thus alleviating the tab filled environment created by the pull tab. Today, virtually all beverages sold in cans are marketed in cans with stay tabs.
Unfortunately however, while the disadvantage of loose tabs was addressed by the advent of the stay tab can, a disadvantage relating to beverage flow from the stay tab can and its predecessors remained. When a fluid is poured from a can opening a vacuum is created within the can which sucks air into the can as the fluid flows out. If a can has one opening, air must flow into that opening as the fluid is poured out of that opening, causing the fluid to exit the can in an uneven, almost violent flow. This uneven flow may cause a carbonated beverage to lose carbonation more quickly than a fluid being poured in a smooth, even flow. Additionally, fluid flowing from a can opening in this manner does so in a messier and slower manner.
One way of creating a smoother, more even flow involves equalizing the pressure between the inside and outside of the can, which may be accomplished by creating a second can opening. Creation of a second can opening can allow air to enter the can via this second opening while fluid leaves the can via the first opening, alleviating the unevenness and violence of the flow discussed above. Unfortunately however, current cans do not provide container top conducive to creating a second can opening.